Phospholipase A.sub.2 (PLA.sub.2) is a protein capable of specifically hydrolyzing 2-acyl ester bond(s) of phospholipids, and includes cytosolic PLA.sub.2 (cPLA.sub.2) and secretory type PLA.sub.2 (sPLA.sub.2) which are clearly distinguishable.
It is known that cPLA.sub.2 can selectively hydrolyze phospholipids containing arachidonic acid which is esterified at the 2-position. Accordingly, the prevention of cPLA.sub.2 activity would inhibit the release of arachidonic acid from phospholipids. Arachidonic acid is a precursor of prostaglandins and leukotrienes, which are biological substances known to be participating in the onset of inflammation. These inflammatory substances are produced through a series of processes so called "arachidonate cascade". Therefore, the inhibition of the release of arachidonic acid would suppress the activity of various substances involved in inflammation and is useful in the prevention or treatment of inflammatory diseases. Examples of such disease include rheumatoid arthritis, asthma, inflammatory bowel disease, injury due to ischemic reperfusion, allergic rhinitis, and psoriasis.
However, there have not been provided any substances which have highly specific activity of inhibiting cPLA2 and are clinically applicable. It has been disclosed that compounds having phenoxy group between thiazolidione and pyrrolidine rings, which pyrrolidine ring is substituted at the N-atom with benzoxazole, etc., are effective on non-insulin dependent diabetes, or the like. See, Japanese Patent Publication (KOKAI) No. 213913/1993 corresponding to France Patent Application, Priority Claiming No. 9110430, Priority date: Aug. 20, 1991. However, there is no description about compounds having phospholipase A.sub.2 inhibitory activity in the said literature.